Hitherto, piezoelectric actuators have been used for the operation of various electronic devices and mechanical elements. Piezoelectric actuators each include a piezoelectric component and external conductors arranged on outer surfaces of the piezoelectric component and used for applying a voltage to the piezoelectric component.
Known examples of the above-described piezoelectric component include single-layer piezoelectric components each composed of a single piezoelectric component; and multilayer piezoelectric components each composed of a plurality of piezoelectric layers stacked. Piezoelectric actuators include piezoelectric components having structures suitable for applications.
The external conductors are usually composed of high-reliability thick-film conductor. In general, each external conductor is formed by applying a conductive paste to a surface of a piezoelectric component and baking the paste, the conductive paste being formed by kneading a metal powder such as a Ag powder, a glass frit, an organic resin binder, and an organic solvent.
In a piezoelectric actuator, a piezoelectric component expands and contracts repeatedly during operation. The piezoelectric component is repeatedly displaced for long-term operation. Thus, a stress due to displacement is repeatedly applied to external conductors. The long-term operation of the piezoelectric actuator may cause fatigue of the external conductor to form a crack in the external conductor, leading to the fracture of the external conductor. The formation of a crack in or fracture of the external conductor impairs the conductivity of the external conductor. As a result, the piezoelectric actuator cannot operate.
To overcome the foregoing problems, Patent Document 1 described below discloses a multilayer piezoelectric part 101 shown in FIG. 6. In the multilayer piezoelectric part 101, internal electrodes 103a and 103b are formed in a multilayer piezoelectric component 102. An external conductor 104 is formed so as to be electrically connected to the internal electrode 103a. 
The external conductor 104 has a structure in which a Ag-wire gauze 104b is embedded in a thick-film conductor 104a mainly composed of a Ag powder. The embedment of the wire gauze 104b increases the mechanical strength of the external conductor 104.
Patent Document 2 discloses a piezoelectric actuator 111 shown in FIG. 7 that is a schematic fragmentary cross-sectional view. The piezoelectric actuator 111 includes an external conductor 113 formed on an outer surface of a multilayer piezoelectric component 112. The external conductor 113 includes an external electrode 114 which is formed directly on the outer surface of the multilayer piezoelectric component 112 and which is composed of a thick-film conductor; and a meshed metal member 115 attached by brazing or welding to the outer surface of the external electrode 114. That is, the netted metal member 115 is contact-connected to the outer surface of the external electrode 114.    Patent Document 1: WO2005/064700 A1    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2003-502870
In the multilayer piezoelectric part 101 described in Patent Document 1, the formation of a crack in the thick-film conductor 104a applies a stress to the wire gauze 104b integrally embedded in the thick-film conductor 104a, thus possibly causing fracture of the wire gauze 104b in association with the crack formed in the thick-film conductor 104a. That is, the wire gauze 104b has an insufficient reinforcing effect.
On the other hand, in the piezoelectric actuator 111 described in Patent Document 2, the meshed wire member 115 is contact-connected to the outer surface of the external electrode 114. However, adhesion by such contact connection is not sufficient. Thus, disadvantageously, the repeated displacement of the multilayer piezoelectric component 112 easily results in detachment at the contact connection. In particular, in the case where the metal member 115 is contact-connected to the external electrode 114 located at the outer surface of a portion in which the piezoelectric component is largely displaced, the external electrode 114 is restricted to contact connection. Thus, after the repetition of displacement, a crack is more easily formed at the portion of the external electrode 114 restricted to contact connection.